The vector function \({\phi }_{\bf {q}} \left( \textbf {\textit {q}} \right)\) ,
is the Joint Score Function (JSF) of the random vector \({\textbf {q}}\)  which is defined as the
gradient of its probability density function [1]}, i.e.,
\(\phi _{\bf {q}} \left( \textbf {\textit {q}} \right) = \nabla _{\textbf {\textit {q}}} \ln p_{\bf {q}} \left( \textbf {\textit {q}} \right)\) 
